The purpose of this project is to test a trend theory that discovers, elucidates and shows the relationships between different factors enabling a drug epidemic to occur. The project will focus on the city of Baltimore, because of prior experience of the project team. While the project will draw on traditional epidemiologic indicators as the starting point, the focus will be on building from those indicators to gather and analyze information that explains why those indicators change in the ways that they do. Such an approach will allow the project to add narrative data from several different types of participants in trend construction, so that various enabling factors can be identified. Comparisons of narratives and indicator data, based on a study of heroin use trends in Baltimore, will be used to construct a trend theory. That theory, in turn, will be tested against a newly emerging trend during the third year of the research. The goal is to develop a theory that explains trends to supplement already available procedures for indicating them.